views: Make view::Views::GetPreferredSize() const.

ui/views/layout/layout_manager.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_LAYOUT_LAYOUT_MANAGER_H_
 #define UI_VIEWS_LAYOUT_LAYOUT_MANAGER_H_
 
 #include "ui/views/views_export.h"
 
 namespace gfx {
@@ skipping 24 matching lines @@
   // host.
   virtual void Uninstalled(View* host);
 
   // Lay out the children of |host| according to implementation-specific
   // heuristics. The graphics used during painting is provided to allow for
   // string sizing.
   virtual void Layout(View* host) = 0;
 
   // Return the preferred size which is the size required to give each
   // children their respective preferred size.
-  virtual gfx::Size GetPreferredSize(View* host) = 0;
+  virtual gfx::Size GetPreferredSize(const View* host) const = 0;
 
   // Returns the preferred height for the specified width. The default
   // implementation returns the value from GetPreferredSize.
-  virtual int GetPreferredHeightForWidth(View* host, int width);
+  virtual int GetPreferredHeightForWidth(const View* host, int width) const;
 
   // Notification that a view has been added.
   virtual void ViewAdded(View* host, View* view);
 
   // Notification that a view has been removed.
   virtual void ViewRemoved(View* host, View* view);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_LAYOUT_LAYOUT_MANAGER_H_